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Old 21st October 2010, 09:33 PM   #1
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Default Aikido transformer coupled output

Hi,

I have built aikido amplifier with output transformer 10k / 150 ohm. I use it as headphone amplifier.
Would there be any benefits converting output stage to white cathode follower to provide lower output impedance and more current drive? Or it is not need with output transformer?

When I plug 150 ohm headphones bass is good, but with 32 ohm headphones bass is weaker. Would white cathode follower provide more bass with 32 ohm headphones?

Thanks.
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Old 21st October 2010, 10:47 PM   #2
bigwill is offline bigwill  United Kingdom
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Increasing C1 will help to give a lower rolloff frequency, since the lower reflected impedance through the transformer will shift the point upwards given the cap stays the same.
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Old 21st October 2010, 11:35 PM   #3
Brit01 is offline Brit01  United Kingdom
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I've built a SRPP type headphone amp just with an output cap (at least 200uF or more), and bass is great even with 32ohms.

Try the cap change as mentioned. Or maybe it's an OPT limitation.

Try without the OPT and replace it with 200-400 uF output cap. Bypassed with a small PIO helps.
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Old 22nd October 2010, 10:16 AM   #4
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Quote:
Originally Posted by Brit01 View Post
I've built a SRPP type headphone amp just with an output cap (at least 200uF or more), and bass is great even with 32ohms.

Try the cap change as mentioned. Or maybe it's an OPT limitation.

Try without the OPT and replace it with 200-400 uF output cap. Bypassed with a small PIO helps.
I have OPT mainly to invert phase back to normal, because aikido already inverts phase.
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Old 22nd October 2010, 10:24 AM   #5
Brit01 is offline Brit01  United Kingdom
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Quote:
I have OPT mainly to invert phase back to normal, because aikido already inverts phase.
If it inverts the phase, what difference to the headphones would this make?
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Old 22nd October 2010, 02:04 PM   #6
45 is offline 45  Italy
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Quote:
Originally Posted by kacernator View Post
Hi,

I have built aikido amplifier with output transformer 10k / 150 ohm. I use it as headphone amplifier.
Would there be any benefits converting output stage to white cathode follower to provide lower output impedance and more current drive? Or it is not need with output transformer?

Thanks.
Be aware of the fact that if you want a White CF with lowest Zout this does not necessarily mean increased current drive. More likely you will find that the highest current output happens for a Zout similar to that of normal CF. So you have to be sure about the extreme case (load, voltage, current..etc) and design the WCF as a consequence.

45
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Old 22nd October 2010, 02:20 PM   #7
Brit01 is offline Brit01  United Kingdom
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What about a SRPP? Output taken from a split top cathode resistor.
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Old 22nd October 2010, 06:30 PM   #8
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Quote:
Originally Posted by Brit01 View Post
If it inverts the phase, what difference to the headphones would this make?
That'd be just fine and won't make any difference at all...as long as you stand backwards!
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Old 22nd October 2010, 06:45 PM   #9
Brit01 is offline Brit01  United Kingdom
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Quote:
Originally Posted by Brit01 View Post
If it inverts the phase, what difference to the headphones would this make?
That'd be just fine and won't make any difference at all...as long as you stand backwards!
If you're using JB's Aikido design then decoupling direct to a set of headphones will be fine. He has this option on his boards.

Can't quite make out what is different about your circuit to require the need to invert the phase with an OPT. Please correct me if I'm wrong.
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Old 22nd October 2010, 07:12 PM   #10
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I dont like the sound when phase is inverted. It just doesnt sound as good. So OPT is easiest method of inverting phase back for me.
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